JPS61271819A - Thin film forming method - Google Patents

Abstract

PURPOSE:To prevent ultraviolet rays from being intercepted owing to the reaction products produced on a plurality of ultraviolet ray transmitting shield plates, by arraying the light transmitting shield plates in a louver board shape, and by introducing non-productive gas from the light source chamber side through the gaps between the respective shield plates. CONSTITUTION:The holder 1' for holding substrates 1 having faces to be treated is mounted near the halogen heaters 3 above the reaction chamber 2. The reaction chamber 2, the light source chamber 5 having the ultraviolet ray source 9 arrayed therein, and the heating chamber 3' having the heaters 3 arrayed therein are kept at a vacuum below 100 torr respectively. Oxide gas and nitride gas being non-productive gas are supplied to the light source chamber 5 and the heating chamber 11 through the flow meters 21 and valves 22, and are introduced into the reaction chamber 2 through the gaps 40 between a plurality of the light transmitting shield plates 10 arrayed in a louver board shape. Moreover, a plurality of the strip shaped plates 11 are arrayed in parallel to the flowing direction 14 of the non-reactive gas, so that reactive gas and reaction products are prevented from being deposited onto the surfaces of the light transmitting shield plates 10 on the side of the reaction chamber. In this way, unrequired reaction products can be prevented from being deposited onto the light transmitting shield plates.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention 1 The present invention is a method for forming a thin film by photochemical reaction. The present invention relates to a CVD (vapor phase reaction) device having means for forming a film without coating it with oil or the like.

4. Prior Art and its Problems Photo-CVD is known as a technique for forming thin films through gas phase reactions, in which a reactive gas is activated by light energy.

This method is superior to the conventional thermal CVD method or plasma CVD method in that it is possible to form a film at a low temperature and does not damage the surface on which it is formed.

When carrying out such a photo-CVD method, an example of the method is shown in FIG.
), heating means (3) for the substrate, and a low-pressure mercury lamp (9) for irradiating light onto the substrate. Doping system (7
) is equipped with a water root bubbler (13) for excitation of the reactive gas, and the exhaust system (8) is equipped with a rotary pump (19). When a reactive gas such as disilane from the doping system is introduced into the reaction chamber (2) and a reaction product such as amorphous silicon is formed on the substrate (substrate temperature 250°C), the ultraviolet light transmitting portion of the reaction chamber is At the same time, a large amount of silicon film is also formed on the shielding plate (10), typically a quartz window. Therefore, in order to prevent the formation of a film on this window, apply Fomblin oil (an example of fluorinated oil) (16
) is thinly coated.

However, although this oil has the effect of preventing the formation of a film on the window (10), it ends up being mixed into the film as an impurity. Furthermore, a reaction product is simultaneously formed little by little on this oil, and the thickness of the film formed is limited due to light absorption there.

Means for Solving Problems j In order to solve these problems, the present invention uses a plurality of shielding plates capable of transmitting ultraviolet light in the photoCVD method as "armor plates" (one chamber (reaction chamber)). A device in which multiple narrow boards are installed at a constant angle for ventilation in a room)
A non-product gas (a gas that does not form a solid by reaction or decomposition, such as HetAr+Hz
, NZ+NH3+NzO, Oz or a mixed gas thereof).

The present invention further provides a "depressurizing means" for lowering the partial pressure (probability of existence) of the reactive gas or active reaction product on or near the surface of the translucent shielding plate on the reaction chamber side of the non-product gas. '', a reaction product is formed on the light-transmitting shielding plate, so that ultraviolet light is not blocked or is not easily blocked.

"Function" Because of these features, when trying to form a film by the photo-CVD method according to the method of the present invention, reaction products are not formed on the plurality of light-transmitting shielding plates or "windows". Or very few. That is, ultraviolet light is always sufficiently transmitted through the window made of synthetic quartz in the form of a "shroud plate" to sufficiently excite the reactive gas (including decomposition and reaction), and to accumulate reaction products on the surface to be formed. . At that time, the same reactive gas and active reaction products are also prevented from flying to the upper surface of the light-transmitting shielding plate, but these products are removed from the reaction space by the pressure reduction means of the present invention. Or the partial pressure in the vicinity can be lowered. Furthermore, the remaining reactive gas and active reaction products flowing back are pushed toward the reaction space by the non-product gas led out to the reaction chamber through the gap between the light-transmitting shielding plates, and the upper surface of the window is covered. I can't arrive. As a result, due to the "partial pressure reduction means" and "leading out of non-product gas through the armor plate-like gap" of the present invention, no reaction products are formed on the surface of the light-transmitting shielding plate, and as a result, Ultraviolet light is emitted with sufficient intensity into the reaction space in which the surface to be formed is disposed in the reaction chamber, and the reactive gas in the reaction space is excited to obtain a reaction solution.

Then, a film can be formed to a sufficient thickness on the surface of the substrate. And conventionally known 100 to 200 people (if oil coating is not performed) or 1000 to 1500 people (
It is possible to repeatedly form a film with a desired thickness in the range of 50 μm to 5 μm, rather than the thickness of the oil coating (in the case of oil coating).

Further, in the present invention, after the CVD, it is possible to produce a film of the same type or a different type on this film in the same batch by plasma CVD using the same reaction chamber. It is also effective to use the plurality of strip-shaped plates themselves, which are the pressure reducing means of the present invention, as one electrode of the plasma CVD method or the plasma etching method.

Further, according to the present invention, unnecessary products deposited on the window due to an insufficient amount of non-product gas being discharged can be removed by plasma etching without exposing the reaction chamber to the atmosphere.

Furthermore, since the apparatus of the present invention is an oil-free reaction system that does not use any Fomblin oil or the like, the degree of vacuum at the background level could be reduced to 10-' torr or less.

A photo-CVD film can be formed by photoexcitation of a semiconductor film such as silicon, an insulating film such as silicon oxide, silicon nitride, or aluminum nitride, or a conductive film made of a metal or its silicide such as metal aluminum, titanium, or tandestene.

``Example'' The present invention will be described in detail below using an example shown in FIG.

In Fig. 2, a substrate (1) having a surface to be formed is held in a holder (1''), and is placed close to a halogen heater (3) (the upper surface of which is water-cooled (32)) above a reaction chamber (2). A reaction chamber (2), a light source chamber (5) in which an ultraviolet light source (9) is disposed, and a heating chamber (3) in which a heater (3) is disposed.
'') were maintained at approximately the same degree of vacuum of 100 torr or less. For this purpose, non-product gases (nitrogen, hydrogen, helium, or argon) that do not interfere with the reaction and do not participate in the reaction were kept at (27 ), and oxide gas (0□, N, O, N
O, No□) or nitride gas (NII3°NzHa,
NFi) from (28) to the flowmeter (21) and valve (22).
) and was supplied to the light source chamber (5) and the heating chamber (11). The non-product gas was then led out (14) into the reaction chamber through gaps (40) between a plurality of light-transmitting shielding plates (lO) arranged in a "shroud-like" manner. Furthermore, a plurality of strip-shaped plates (11), which are one of pressure reduction means, are used to extract non-reactive gas (14).
was arranged parallel to (along) the direction of , to prevent reactive gas and reaction products on the reaction chamber side from adhering to the surface of the light-transmitting shielding plate (10). In particular, reactive gases and reaction products can reach the surface of the shielding plate (10) or its vicinity by causing the gas that is intended to fly (backward) toward the shielding plate (10) to be deposited on the surface of this means by means of reduced partial pressure. could be prevented.

In this embodiment, among the reactive gases, a product gas (gas that decomposes and forms a post-reaction body) is passed through the nozzle (30).
It was led out (31) further into the reaction space (1°).

For example, when producing a semiconductor such as silicon as a reaction product, the product gas is silane (Si), which is a silicide gas.
nllzn-z), silicon fluoride (SiF2.SiF4.5
izF,.

HlSih) was used. Furthermore, hydrogen, argon, or helium was used as a non-product gas and was supplied from (27).

When producing nitrides (silicon nitride, aluminum nitride, gallium nitride, indium nitride, antimony nitride) as reaction products, 5 iJ each as a product gas.
b, AI(Hs)3. Ga(C)Is)t, In(C
Hs)*.

5n(CHs)4,5b(CH3)s was used and supplied from (2). Ammonia or hydrazine was also supplied from (27) as a non-product gas participating in the reaction. In addition, a non-product gas (hydrogen or helium) that does not participate in the reaction was supplied as a carrier gas from (24) and (28).

When producing an oxide (silicon oxide, aluminum oxide, indium oxide, tin oxide, antimony oxide, or a mixture thereof) as a reaction product, the oxide (NtO.

0□, NO or N(h) were used and supplied from (27). In this case, silicide (Si
Jh.

5izFb), aluminum compound (A I (Cll
a) 3) Indium compound (In(CH:+)
! + InC1z), stannide (SnC14゜5n
(CHs)t), antimonide (Sb(CH:+)s
, 5bc1z) was used and supplied from (23). Hydrogen or helium as a non-product gas not participating in the reaction was supplied as a carrier gas from (25).

When making conductors (aluminum, tungsten, molybdenum, titanium, or their silicides), hydrogen, argon, or helium was used as the non-product gas. Al(CHx)z respectively as product gas.

WF, MoCl5. TiCl4 or them and 5i84.
5iHz+5iHzC1z+SiF, (2
3) and (24).

Hydrogen, a non-product gas that does not participate in the reaction (27)
and (25) were supplied as a carrier gas.

The pressure in the reaction chamber is controlled by a control valve (17).

A turbo molecular pump (Osaka Vacuum P
using G550) (18), rotary pump (19)
This was accomplished by exhausting the air.

When the preliminary chamber is evacuated using the cock (20), the exhaust system (8) is opened on that side and closed on the reaction chamber side. Furthermore, when the reaction chamber was evacuated or a photochemical reaction was performed, the reaction chamber side was opened and the preliminary chamber side was closed.

The film formation process used a load-lock method in which no pressure difference was created in moving the substrate from the preliminary chamber to the reaction chamber. First, the substrate (1) and holder (lo) are inserted and arranged in the preliminary chamber (4), and after vacuuming,
Open the gate valve (6) between the reaction chamber (2) which has been evacuated to 10-'torr or lower in advance,
Transfer the substrate (1) and holder (1゛) to the reaction chamber (2), close the gate valve (6), and open the reaction chamber (axis) and preliminary chamber (4).
) were separated from each other.

After that, in order to prevent reactive gases from entering the light source chamber due to backflow, first add 100 to 150% of the non-product gas.
It was introduced into the light source chamber at a flow rate of 00 cc/min, and was also supplied to the connected heating chamber at the same time. They are then led out (14) into the reaction chamber through gaps (40) between a plurality of "armor plate-like" shielding plates (10). After that, the reactive gas (31) is introduced into the nozzle (
30).

In this example, the "armor plate-like" translucent shielding plate is made of synthetic quartz, and is 3 cm (width) x 34 cm (length).
x2mm (thickness), and each is 3IlIIm from each other.
Superimposed.

The gap (40) was 0.1 mm. The pressure reducing means is a metal plate with a height of 1.5 cm and a length of 34 cm.
I11 were placed, for example, 10 mm apart. As a result, the average wind speed in the gap (40) is 3 torr, and the pressure in the reaction chamber is 3 torr.
Derivation of gas at 100 cc/min results in lllI minutes. As a result, the wind speed (50 cm/min to 5 cm
0 m/min).

The light source for the reaction was a low-pressure mercury lamp (9) made of a synthetic quartz tube, and water cooling (32') was provided. The ultraviolet light source was a low-pressure mercury lamp made of synthetic quartz (emitting wavelengths of 185no+, 254n-, emission length 40CI11, irradiation intensity 20+++W/cm).
, lamp power 45-) number of lamps is 16.

This ultraviolet light passes through the "shroud" quartz (10), which is a transparent shielding plate made of synthetic quartz, and passes through the reaction section (2) of the reaction chamber (2).
2) Irradiate the reactive gas (31) in the substrate (1) and the formation surface (1') of the substrate (1).

The heater (3) is a "deposition up" type located above the reaction chamber (2) to prevent flakes from adhering to the surface to be formed and causing pinholes, and to
1) was heated from the back side to a predetermined temperature (room temperature to 700°C) using a halogen heater.

The reaction chamber was made of stainless steel, and the ultraviolet light source was also kept in a reduced pressure atmosphere in a stainless steel container surrounding the light source chamber and the reaction chamber, which were kept under vacuum. Therefore, a coating can be formed on a substrate with a size of 30 ca+ x 30 cm without any industrial problems, instead of on a small coating area of 5 cm x 5 cm.

FIG. 3 is an enlarged perspective view of only the light-transmitting shielding plate and the pressure reducing and dividing means in FIG. 2.

In addition, the A-A' cross section and the B-8' cross section are shown in Figure 4 (A).
, shown in (B). FIG. 4(B) shows the relative flow velocity distribution of non-product gas derived from the gap in the strip-shaped plate that is the pressure reducing means and the fact that the active reaction product or reactive gas flows back toward the shielding plate. It also shows the direction of flow when it is put away.

As is clear from the perspective view in FIG.
0-1), (10-2), and (10-3).

Furthermore, in the present invention, a plurality of strip-shaped plates (
11-1), (11-2), and (11-3), the direction perpendicular to the surface of the shielding plate (10) (vertical direction in the drawing)
It was configured as follows. Thereby, they are arranged at a constant distance (42) from each other. Here, one strip having an interval of 10 cm had a height of 15III+ and a width of 34 cm. As a result, the active reaction products are (41), (41')
, and the adhesion on the surface of this pressure reducing means is promoted. As a result, it is possible to prevent the product gas and products from reaching the upper surface of the drawing plate (10) with much higher efficiency than when there is no pressure reducing means. As a result, the flow rate in the gap was 3 (1 m/sec) when there was no pressure reducing means, but the consumption of non-reactive gas, which required a high speed of 30+ a/min, was reduced to about 10 -100 m/sec. I was able to save money.

That is, as shown in FIG. 4(B), the gas led out from the gap is close to the pressure reducing means at its relative flow velocity.
In (14-1) and (14-3), the flow velocity is slow, and the central part (
14-2) is fast. As a result, the reaction product or reactive gas moves from the center toward the pressure reducing means as shown by the arrows (41) and (4
1°). A large amount of the reactive gas adheres to the surface of the strip-shaped plate, and can be prevented from adhering to the synthetic quartz plate.

Further, specific examples according to the present invention are shown in Experimental Examples 1 to 4 below.

Experimental example 1...Example of forming a silicon nitride film In Fig. 2, ammonia was used as a reactive gas at 50
cc/min, disilane was supplied from (23) at 8 cc/min, and the substrate temperature was set at 250°C. The substrates were four 5-inch diameter wafers. The internal pressure of the reaction chamber (2) was set at 3, Qtorr.

Nitrogen is used as a non-product gas that does not participate in the reaction.
cc/min and ammonia, a non-product gas that can participate in the reaction, at 200 cc/min, respectively (27), (28
) was introduced. In that case, it was flowed at an average flow rate of 1017 minutes. As a result, it was possible to prevent silicon nitride from adhering to the upper surface of the armor plate-like shielding plate.

A 1,500-layer thick silicon nitride film was formed on the substrate in a 30-minute reaction. The film formation rate was 50 people/min. The present invention uses direct optical excitation without using mercury vapor or the like.

The variation of the 5 points of the coating was within ±10%.

In addition, in the case where a pressure reducing means was not provided, a flow rate of 30 mm/sec was required to prevent adhesion to the surface of the armor plate. As a result, the pumping speed of the device was close to its limit. However, by providing pressure reducing means in addition to this armor plate-like shielding plate, it has become possible to reduce the flow of gas for preventing adhesion to about 1/10 as described above.

Of course, the interval (42) between the strip-like plates of this pressure reducing and dividing means is set to 1
If 5ms+ is set from 0s+s, the flow velocity from the gap is 5-7
Now it is possible to reduce the amount even further.

Experimental Example 2: Formation of silicon oxide film A silicon oxide film was formed under the same conditions as in Experimental Example 1. However, NtO is used as a non-product gas taking part in the reaction derived from the light source chamber.
Used instead of 3.

And from (25) and (26) each 50cc/
min and 300 cc/min. As a result, they were able to make a silicon oxide film the thickness of 5,000 people in one hour. At this time, P) 13°B and H may be added at the same time to form phosphorus glass or boron glass.

Experimental Example 3 Formation example of amorphous silicon film Disilane (SiJ&) was supplied from (23) at a flow rate of 100 cc/min. Further, hydrogen was supplied from (28) at a flow rate of 500 cc/min to prevent it from adhering to the upper surface of the "armor plate-like" shielding plate. The temperature was 210° C. and the reaction chamber pressure was 10 torr. A film thickness of 2,500 layers could be formed on the surface to be formed in 60 minutes of deposition.

Even if the same process is repeated, the same film thickness of 2300~2
We were able to get 700 people.

Experimental example 4... Formation example of aluminum nitride Al(CH
3) Methyl aluminum with 3 as a representative example (23)
It was supplied at a rate of 30 cc/min. 30 hydrogen from (24)
Diluted at cc/min. Also, from (28), ammonia is
00 cc/min. As a result, the methyl aluminum decomposed without introducing mercury vapor into the light source chamber, and it was possible to create an aluminum nitride film 1,300 times thick.

Film formation rate was 30 people/min (pressure 3 torr).

The temperature was 350°C). Other alkyl compounds such as ethylaluminum Al (CJs) 3 may also be used.

Experimental Example 5: Formation of metallic aluminum In Experimental Example 3, hydrogen was added at 30% each from (24) and (28).
cc/min, at a flow rate of 300 cc/min. After 3 hours of deposition, a metal aluminum layer with a thickness of approximately 500 mm was obtained on the surface to be formed. The rest was the same as in Experimental Example 3.

"Effects" As is clear from the above description, the present invention, when forming a film on a large-area substrate, eliminates the unnecessary reaction-generated film on a light-transmitting shielding plate by using this plate in the form of a plurality of "armor plate-like" More complete removal can be achieved by using a shielding plate and also installing a partial pressure reducing means on the side of the reaction chamber. In addition, the flow rate of the non-product gas flowing into the reaction chamber through the gap between the armor plates is 1
I was able to save up to /10. Therefore, there is no need to use any oil on the top surface of the window. Therefore, it is difficult for impurities such as carbon to enter the coating, and the exhaust pressure is reduced to 1O-1t.
It is possible to create a high vacuum of 100 mA, and it is now possible to produce an oil-free, high-purity film.

Furthermore, by removing flakes that fell onto the top surface of the window using plasma etching in the same reaction chamber, we created a completely oil-free environment in the reaction chamber, making continuous formation possible for the first time.

Note that the present invention applies to many types of semiconductors shown in Example 1,
Insulators and conductors can be formed using the same technical idea. It is also effective to form a magnetic film of iron, nickel, cobalt, or a compound thereof by using a carbonylated product of iron, nickel, or cobalt, which is not shown above, as a reactive gas.

In the experimental examples described above, dopants can be added at the same time when forming a silicon semiconductor. Also, the light source is not a low-pressure mercury lamp but an excimer laser (wavelength 100 to 400 nm).
It goes without saying that , argon laser, nitrogen laser, etc. may be used in place of or in combination with the low-pressure mercury lamp.

In the present invention, the film growth rate may be improved by passing the film through a mercury bubbler.

In an experimental example of the present invention, a shielding plate in the form of an armor plate was arranged to be tilted from one side, in FIG. 2, from the lower right side to the upper left side. However, this may be a shroud plate in which the nozzle is disposed in the center and a shielding plate is disposed tilted upward from the center to the left and right. In that case, the shape of the pressure reducing means is as shown in Fig. 2. Similarly, if the gas flow is directed in that direction from the center toward the outer periphery, and conversely, if the center is concentrically arranged from the center, a brittle plate-shaped shield plate is installed concentrically from the outside. All you have to do is set up the . The pressure reducing and dividing means must be arranged radially outward from the center.

In FIG. 2, the light source was set downward and the reaction direction was set upward. However, it is also possible to arrange the reaction space on the lower side. Further, the light sources may be arranged laterally.

[Brief explanation of the drawing]

FIG. 1 shows a conventionally known photoexcited CVD apparatus. FIG. 2 shows a CVD apparatus of the present invention. FIG. 3 shows an enlarged perspective view of the shielding plate and pressure reducing means of the present invention. Fig. 4 shows a vertical cross-sectional view taken along lines A-A'' and B-B' in Fig. 3. 2a of gl

Claims (1)

[Scope of Claims] 1. A light source for excitation of a reactive gas and a reaction chamber in which a substrate having a surface to be formed is disposed, and between the light source and the reaction chamber are divided into a plurality of sections. In a thin film forming apparatus having a light-transmitting shielding plate disposed at A method for forming a thin film, characterized in that reaction products are prevented from adhering to the light-transmitting shielding plate, or are made difficult to adhere to the light-transmitting shielding plate, by guiding the reaction product through the gap between the light-transmitting shielding plates to the reaction chamber side. 2. In claim 1, by arranging a plurality of light-transmitting light-shielding plates in the form of armor plates, the non-product gas is led out along the surface of the light-transmitting light-shielding plates on the reaction chamber side. A thin film forming method characterized by: 3. In claim 1, a plurality of strip-shaped plates are provided in a direction that does not impede the flow of the non-product substrate derived as means for reducing the partial pressure of the reactive gas on the surface of the transparent shielding plate. A method for forming a thin film, characterized in that: are arranged at a distance from each other.